JP2013067861A - Oxygen-consuming electrode and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen-consuming electrode in which problems of prior art are solved, and silver oxide is used particularly for use in chlor-alkali electrolysis so that a low operating voltage in chlor-alkali electrolysis is attained; and a method for manufacturing the same.SOLUTION: The method of manufacturing the oxygen-consuming electrode includes a step (a) of adding an aqueous solution of sodium hydroxide and a solution of silver nitrate simultaneously to a receiver while maintaining a pH value constant in a range from 10 to 12, and maintaining a temperature in a range from 20 to 80°C to precipitate silver oxide using a mechanical stirrer for introducing stirring energy in a range from 0.01 to 10 W/L, a step (b) of taking out the precipitated silver oxide resulting in the step (a) from the suspended liquid, a step (c) of drying the silver oxide optionally under a reduced pressure and optionally in an inert gas atmosphere, and at a temperature in a range from 80 to 200°C, and a step (d) of further fabricating the resulting silver oxide together with a conductive support material, a silver particle-containing catalyst and a particulate fluorinated polymer to form a planar oxygen-consuming electrode.

Description

  The present invention relates to an oxygen-consuming electrode and an electrolysis device comprising a novel catalyst coating based on silver and finely divided silver oxide, especially for use in chlor-alkali electrolysis. The invention further relates to a method for producing an oxygen consuming electrode and the use of the oxygen consuming electrode in chlor-alkali electrolysis or fuel cell technology.

  The present invention takes the form of a gas diffusion electrode and typically starts from an oxygen consuming electrode known per se, comprising a conductive support and a gas diffusion layer comprising a catalytically active component.

  Various attempts to produce and operate oxygen consuming electrodes in electrolytic cells on an industrial scale are basically known from the prior art. The basic idea is to replace the hydrogen generating cathode in electrolysis (eg chlor-alkali electrolysis) with an oxygen consuming electrode (cathode). A review of possible electrolysis cell designs and methods can be found in Moussallem et al., “Chlor-Alkali Electrolysis with Oxygen Depolarized Cathodes: History, Present Status and Future Prospects”, J. Appl. Electrochem. 38 (2008) 1177-1194. It is done.

An oxygen-consuming electrode (hereinafter also referred to as OCE for short) must satisfy a series of requirements in order to be used in an industrial electrolysis cell. For example, the catalyst used and all other materials must be chemically stable to about 32 wt% sodium hydroxide solution and pure oxygen, typically at temperatures of 80-90 ° C. At the same time, since the electrode is usually operated by being incorporated in an electrolytic cell having an area (industrial scale) exceeding 2 m ² , a high degree of mechanical stability is required. Further properties are: high electrical conductivity, small layer thickness, large internal surface area, and high electrochemical activity of the electrocatalyst. Hydrophobic and hydrophilic pores suitable for conducting gases and electrolytes and corresponding pore structures are required so that the gas and liquid spaces remain impermeable to the extent that they remain separated from each other. The Long-term stability and low manufacturing costs are further specific requirements for industrially usable oxygen-consuming electrodes.

  The oxygen consuming electrode typically consists of a support element (eg, a porous metal plate or wire mesh) and an electrochemically active coating. The electrochemically active coating is microporous and consists of a hydrophilic component and a hydrophobic component. The hydrophobic component makes electrolyte penetration difficult and thus keeps the corresponding pores from clogging due to the migration of oxygen to the catalytically active site. The hydrophilic component allows the electrolyte to penetrate the catalytically active site and allows the hydroxide ions to leave. The hydrophobic component used is generally a fluorinated polymer such as polytetrafluoroethylene (PTFE), and in addition, it serves as a polymer binder for the catalyst. In the case of an electrode having a silver catalyst, silver serves as a hydrophilic component. In the case of a carbon-supported catalyst, the support used is carbon with hydrophilic pores, and the liquid can move through the hydrophilic pores.

  Oxygen is reduced in the three-phase region where the gas phase, liquid phase and solid catalyst are in contact.

  The gas moves through the pores in the hydrophobic matrix. The hydrophilic pores are filled with liquid, water moves to the catalytic site, and hydroxide ions leave the catalytic site through the hydrophilic pore. Since oxygen only dissolves to some extent in the aqueous phase, water-free pores must be sufficiently available for oxygen to move.

  A number of compounds have been described as oxygen reduction catalysts.

  For example, there are reports of using palladium, ruthenium, gold, nickel, transition metal oxides and sulfides, metal porphyrins and metal phthalocyanines and perovskites as oxygen consuming electrode catalysts.

  However, only platinum and silver are really important as catalysts for reducing oxygen in alkaline solutions.

  Platinum has a very high catalytic activity for the reduction of oxygen. Since platinum is expensive, it is used exclusively in a supported form. A known and proven support material is carbon. Carbon carries current through the platinum catalyst. The pores of the carbon particles may be made hydrophilic by oxidation of the carbon surface so as to be suitable for water movement. However, the stability of the carbon-supported platinum electrode during long-term operation is probably inadequate, probably because platinum also catalyzes the oxidation of the support material. Oxidation of the support material results in a loss of mechanical stability of the electrode.

  Silver also has a high catalytic activity for oxygen reduction.

  According to the prior art, silver may be used with carbon as a support or in the form of finely divided metallic silver.

An OCE comprising carbon-supported silver typically has a silver concentration of 20-50 g / m ² . Carbon-supported silver catalysts are basically more durable than the corresponding platinum catalysts, but the long-term stability of carbon-supported silver catalysts under chlor-alkali electrolysis conditions is limited.

Moussallem et al., "Chlor-Alkali Electrolysis with Oxygen Depolarized Cathodes: History, Present Status and Future Prospects", J. Appl. Electrochem. 38 (2008) 1177-1194

  The object of the present invention is to eliminate the above-mentioned drawbacks, in particular, silver oxide for use in chlor-alkali electrolysis, an oxygen-consuming electrode capable of low operating voltage in chlor-alkali electrolysis, and The manufacturing method is provided.

Surprisingly, it has been found that the use of silver oxide prepared from the following process as a catalytically active material in a gas diffusion electrode results in a low cell voltage in chlor-alkali electrolysis:
(1) A step of precipitating silver oxide in an aqueous sodium hydroxide solution (this step maintains a pH within a range of 10 to 12, preferably 11 and a temperature of 20 ° C. to 80 ° C., preferably 30 Including using a suitable stirrer (especially a propeller stirrer) at a stirrer speed of 300-1000 rpm to introduce the predetermined stirrer energy while maintaining within the range of C-70C,
(2) Filtration and washing the filter cake (this step is repeated more than once if necessary. After the last washing, the suspension is filtered once more),
(3) A production method selected by drying the filter cake in an inert gas (eg, nitrogen or noble gas) atmosphere in a drying chamber at a temperature in the range of 80 ° C. to 200 ° C., optionally under reduced pressure (5 to 1000 mbar). A step of further processing the silver oxide formed by the step of obtaining OCE.

Aspects of the present invention include
a) While maintaining the pH constant within a range of 10-12 and maintaining the temperature within a range of 20 ° C to 80 ° C, an aqueous sodium hydroxide solution and a silver nitrate solution were simultaneously added to the receiver, and 0.01 W Precipitating silver oxide by using a mechanical stirrer to introduce stirring energy in the range of / L to 10 W / L;
b) removing the precipitated silver oxide of step a) from the suspension;
c) drying the silver oxide at a temperature in the range of 80 ° C. to 200 ° C., optionally under reduced pressure and optionally under an inert gas atmosphere;
d) A method for producing an oxygen-consuming electrode, comprising a step of further processing the obtained silver oxide together with a conductive support material, a silver particle-containing catalyst and a finely powdered fluorinated polymer to form a planar oxygen-consuming electrode.

  Another embodiment of the present invention is the above method wherein energy is introduced using a propeller stirrer in step a).

  Another embodiment of the present invention is the above process, wherein the energy input in step a) is 0.01-1 kWh per kg of precipitated product.

  Another aspect of the present invention is the above process, wherein the pH of the mixture is maintained in the range of 10.5 to 11.5 in step a).

  Another embodiment of the present invention is the above process, wherein in step a) the temperature of the mixture is maintained within the range of 30 ° C to 70 ° C.

  Another embodiment of the present invention is the above process, wherein the silver oxide of step c) has a d90 of less than 13 μm.

  Another aspect of the invention is that in further processing step d) 0.5-20 parts by weight of fluorinated polymer, 1-20 parts by weight of particulate silver and 60-98.5 parts by weight of particulate silver oxide Wherein said method is used.

  Another aspect of the present invention is the above process, which uses a dry production process in a further processing step d).

  Yet another aspect of the present invention is an oxygen consuming electrode comprising a gas diffusion layer comprising a conductive support, an electrical contact site, and a catalytically active component, manufactured by the above method, The layer is an oxygen consuming electrode comprising at least one fluorinated polymer, particulate silver and particulate silver oxide.

  Another aspect of the present invention is the oxygen consuming electrode comprising silver oxide particles having a d90 of less than 13 μm.

  Yet another embodiment of the present invention is an electrolytic cell for hydrolyzing an alkali metal chloride, comprising the oxygen-consuming electrode as a cathode.

  Another aspect of the present invention is that the stirring energy is in the range of 0.05 W / L to 5 W / L, and the suspended silver oxide of step a) is suspended by filtering the suspension and washing the silver oxide one or more times. It is the said method taken out from a turbid liquid.

  Another embodiment of the present invention is the above method, wherein the stirring energy is in the range of 0.1 to 2 W / L.

  Another embodiment of the present invention is the above method, wherein the propeller stirrer is operated at a stirring speed of 300 to 1000 rpm.

  Another embodiment of the present invention is the further processing step d) wherein 2-10 parts by weight of fluorinated polymer, 2-10 parts by weight of particulate silver and 70-95 parts by weight of particulate silver oxide are used. Is the method.

  Another aspect of the present invention is by pressing a fine powder mixture of silver oxide, silver particle containing catalyst and fine powder fluorinated polymer together with a conductive support material in a further processing step d) to form a planar oxygen consuming electrode. Said method using a dry production process.

  Another aspect of the present invention is the electrolysis cell, wherein the alkali metal chloride is selected from the group consisting of sodium chloride, potassium chloride and mixtures thereof.

  Another aspect of the present invention is the electrolytic cell, wherein the alkali metal chloride is sodium chloride.

The present invention
a) While maintaining the pH constant within a range of 10-12 and maintaining the temperature within a range of 20 ° C to 80 ° C, an aqueous sodium hydroxide solution and a silver nitrate solution were simultaneously added to the receiver, and 0.01 W Oxidation by using a mechanical stirrer to introduce stirring energy in the range of / L to 10 W / L, preferably 0.05 W / L to 5 W / L, more preferably 0.1 W / L to 2 W / L A step of precipitating silver,
b) removing the precipitated silver oxide of step a) from the suspension, in particular by filtering the suspension one or more times and washing the silver oxide;
c) optionally drying the silver oxide at a temperature in the range of 80 ° C. to 200 ° C. under an inert gas atmosphere or / and under reduced pressure,
d) A method for producing an oxygen-consuming electrode comprising the step of further processing the obtained silver oxide together with a conductive support material, a silver particle-containing catalyst and a finely powdered fluorinated polymer to form a flat oxygen-consuming electrode.

  Suitable inert gases are, for example, nitrogen or noble gases.

  Preferred is the method wherein the silver oxide of step c) has a d90 of less than 13 μm. The present invention also provides an oxygen consuming electrode comprising at least a gas diffusion layer comprising a conductive support, an electrical contact site, and a catalytically active component produced by the method of the present invention. Also provides an oxygen consuming electrode comprising at least one fluorinated polymer, particulate silver and particulate silver oxide.

  Advantageously, in step a), the energy is preferably introduced using a propeller stirrer, particularly operating at a stirring speed of 300 to 1000 rpm.

  Particularly preferably, the energy input in step a) is 0.01 to 1 kWh per kg of precipitated product.

  A preferred embodiment of the novel process is characterized in that the mixture in step a) is maintained within a pH range of 10.5 to 11.5.

  In another preferred embodiment of the invention, the temperature of the mixture in step a) is maintained within the range of 30 ° C to 70 ° C.

  It is particularly preferred to carry out the process so that the silver oxide of step c) has a d90 of less than 13 μm.

  An oxygen-consuming electrode characterized by comprising silver oxide particles having a d90 of less than 13 μm is preferred.

  Another particularly preferred embodiment of the novel process is that in a further processing step d) 0.5-20 parts by weight, preferably 2-10 parts by weight of fluorinated polymer, 1-20 parts by weight, preferably 2-10 parts by weight. It is characterized in that part by weight of particulate silver and 60-98.5 parts by weight, preferably 70-95 parts by weight of particulate silver oxide are used.

  It is preferable to use unsupported silver as the catalyst. In the case of an OCE comprising a catalyst made of unsupported metallic silver, the stability problem due to the decomposition of the catalyst carrier does not naturally occur.

  In the process for producing OCE comprising an unsupported silver catalyst, silver is preferably introduced at least partially in the form of silver oxide and then reduced to metallic silver. The reduction of the silver compound also changes the crystal arrangement, in particular forming bridges between the individual silver particles. This strengthens the structure as a whole.

  The method for producing an oxygen consuming electrode comprising a silver catalyst can basically be classified into a wet production method and a dry production method.

  In the drying method, a mixture of catalyst and polymer component (usually PTFE) is ground into fine particles, then distributed on a conductive support element and pressed at room temperature. Such a method is described, for example, in EP 1728896 A2.

  Wet manufacturing uses pastes or suspensions consisting of catalyst and polymer components in water or other liquids. In the process of preparing the suspension, a surfactant can be added to increase the stability. The paste is then applied to the support by screen printing or calendering, and the less viscous suspension is typically sprayed onto the support. The support with the applied paste or suspension is dried and sintered. Sintering is performed at a temperature near the melting point of the polymer. Further, after sintering, the OCE may be strengthened at a temperature higher than room temperature (up to the melting point, softening point or decomposition point of the polymer).

  The electrode manufactured by these methods is incorporated in an electrolytic cell without previously reducing silver oxide. After the electrolytic cell is filled with the electrolytic solution, silver oxide is reduced to metallic silver under the action of an electrolytic current.

Various publications describe methods for preparing silver oxide based on precipitation using silver nitrate and sodium hydroxide solutions. For example, US 771872 B2 describes a method for making and using silver oxide powder for button cells. This manufacturing method essentially consists of four steps. The aqueous silver nitrate solution and sodium hydroxide solution are mixed and then allowed to settle by stirring for a long time of at least 30 minutes (12 hours in the example with the best performance), the suspension is filtered and then under reduced pressure. Dry at high temperature. The powder thus produced has a d50 value of 1 to 500 μm and a BET surface area of 5 m ² / g. The disadvantage of this production method is an extremely long stirring time. This considerably increases the manufacturing time in the manufacturing method on an industrial scale. Another disadvantage is that the individual particles can coalesce within such a long agitation time. This can result in large diameter particles (greater than 50 μm), which can result in undesirably high pressing in subsequent further processing, for example in rolling OCE manufacturing methods as described in EP 1728896. .

US 2005050990 describes another method for producing silver oxide microparticles. In this method, a dispersant is added during precipitation, or sodium hydroxide solution and silver nitrate solution for precipitation are metered simultaneously into the initial introduction of sodium hydroxide solution. In these cases, after precipitation, filtration and drying, the powder is subjected to wet grinding. This results in silver oxide particles having a d50 of less than 3 μm and a d90 of less than 8 μm and a BET surface area of greater than 0.9 m ² / g. Both described methods have disadvantages compared to the method of the present invention. In the first method, a dispersant must be added additionally and later removed again. In the second method, the two solutions must be metered at the same time, and metering is complicated. The wet grinding method also includes further processing steps.

  In the present invention, “d50” means the diameter of the volume-based particle size distribution in which 50% of the total measured particle size of the particle size distribution is less than or equal to this value. Typically, the particle size distribution is measured using a laser diffraction spectrometer (eg MS 2000 Hydro S). During the measurement, the powder is typically in the form of a dispersion in water with the addition of a surfactant (eg Tween 80). The dispersing step is typically performed by sonication with a duration of 15 to 300 seconds. The term “d90” likewise corresponds to the diameter of the volume-based particle size distribution, in which 90% of the total measured particle size of the particle size distribution is below this value.

In the present invention, “BET surface area” means a specific surface area (unit: m ² / g) of a solid measured according to DIN ISO 9277.

  Silver oxide-containing oxygen-consuming electrodes are produced in particular by the previously described techniques known per se, for example in wet or dry production processes. In the present invention, it is preferable to use a dry production method. This is because the dry production method does not require an intermediate sintering step.

  In a particularly advantageous embodiment of the invention, the novel process comprises in a further processing step d), in particular a fine powder mixture of silver oxide, a silver particle-containing catalyst and a finely divided fluorinated polymer, pressed with a conductive support material, It is configured to use a dry manufacturing method by forming a consumption electrode.

  The present invention also provides an oxygen consuming electrode comprising at least a gas diffusion layer comprising a conductive support, an electrical contact site, and a catalytically active component, produced by the novel method of the present invention described above. There is also provided an oxygen consuming electrode wherein the gas diffusion layer comprises at least one fluorinated polymer, particulate silver and particulate silver oxide.

  The composition of the oxygen consuming electrode is preferably 0.5 to 20 parts by weight, preferably 2 to 10 parts by weight of fluorinated polymer, 1 to 20 parts by weight, preferably 2 to 10 parts by weight, as described above. And 60 to 98.5 parts by weight, preferably 70 to 95 parts by weight of particulate silver oxide.

  A preferred embodiment of the novel oxygen consuming electrode is characterized in that the oxygen consuming electrode comprises silver oxide particles having a d90 of less than 13 μm.

  The novel oxygen-consuming electrode is preferably connected as a cathode, particularly in an electrolysis cell for hydrolyzing alkali metal chlorides (preferably sodium chloride or potassium chloride, more preferably sodium chloride).

  Alternatively, the oxygen consuming electrode can preferably be connected as the anode in the fuel cell.

  Accordingly, the present invention further relates to the use of a novel oxygen consuming electrode to reduce oxygen under alkaline conditions, particularly in alkaline fuel cells, for example novel oxygen consumption in drinking water treatment to prepare sodium hypochlorite. The use of an electrode or in particular a novel oxygen-consuming electrode in chlor-alkali electrolysis for electrolyzing LiCl, KCl or NaCl is provided.

  The novel OCE is more preferably used in chlor-alkali electrolysis, and in the present invention particularly in sodium chloride (NaCl) electrolysis.

  Accordingly, the present invention further provides an alkali metal chloride (preferably sodium chloride or potassium chloride, more preferably sodium chloride), characterized in that it comprises the oxygen-consuming electrode of the present invention described above as a cathode. An electrolytic cell for decomposition is also provided.

  The invention is illustrated in detail by the following examples, which are not intended to limit the invention.

  All of the references cited above are hereby incorporated by reference in their entirety for all useful purposes.

  While particular structures have been shown and described which specifically illustrate the present invention, those skilled in the art can make various modifications and reconfigurations thereof, without departing from the spirit and scope of the inventive concepts, and It will be apparent that the invention is not limited to the specific embodiments shown and described herein.

Example 1
First, an aqueous sodium hydroxide solution having a concentration of 120 g / L and an aqueous silver nitrate solution having a concentration of 2.6 mol / L were prepared. The two starting solutions were metered into the batch reactor stirred at 800 rpm with a propeller stirrer at 60 ° C. within 2 hours at a rate such that the pH was maintained at 11.2. The total volume of the batch reactor was 1.5L. The mixture was stirred at the same temperature for an additional 15 minutes.
The suspension was then filtered and the filter cake was washed repeatedly and then dried.
The powder thus prepared was measured for d90 of 12.7 μm after sonication (5 minutes in an ultrasonic bath).

  Each time 0.16 kg of a powder mixture consisting of 7% by weight of PTFE powder of Dyneon TF2053Z type, 86% by weight of silver (I) oxide prepared by the method described above, and 7% by weight of Ferro 331 type of silver powder was each time in an IKA mixer. Mixed 4 times for 15 seconds. During operation, the temperature of the retained powder mixture was less than 50 ° C. After mixing, the powder mixture was sieved with a mesh having a mesh size of 1.0 mm.

  The sieved powder mixture was then applied to a nickel wire mesh with a wire thickness of 0.14 mm and a mesh size of 0.5 mm. Application was carried out using a template having a thickness of 2 mm, and powder was applied using a sieve having a mesh size of 1 mm. Excess powder charged beyond the thickness of the template was removed using a skimmer. After removing the template, the support with the applied powder mixture was pressed using a roller press with a pressure of 0.26 kN / cm. The oxygen consuming electrode was removed from the roller press.

The oxygen consuming electrode thus produced was used in the electrolysis of a sodium chloride solution (concentration 210 g / L) with a DuPONT N982WX ion exchange membrane and a gap of 3 mm containing sodium hydroxide solution between the OCE and the membrane. . The temperature of the electrolytic solution was 90 ° C., and the concentration of the sodium hydroxide solution was 32% by weight. Oxygen having a purity of 99.5% was metered into the side of the OCE that did not face the gap containing sodium hydroxide solution. The anode used was expanded titanium metal (manufacturer: De Nora, LZM type) coated with a mixed noble metal oxide containing ruthenium. The active electrode base region and the membrane base region were each 100 cm ² . The sodium hydroxide solution stream and the sodium chloride stream were each 5-10 L / hr and the oxygen stream was 45-55 L / hr.

A cell voltage of 2.03 V was measured at a current density of 4 kA / m ² .

Comparative Example 1 (standard commercial silver oxide)
0.16 kg of a powder mixture consisting of 7% by weight of Dyneon TF2053Z type PTFE powder, 86% by weight of silver oxide (I) (batch number 1828785) from Umicore Brazil, and 7% by weight of Ferro 331 type silver powder was each time in an IKA mixer. Mixed 4 times for 15 seconds. During operation, the temperature of the retained powder mixture was less than 50 ° C. After mixing, the powder mixture was sieved with a mesh having a mesh size of 1.0 mm.

  The sieved powder mixture was then applied to a nickel wire mesh with a wire thickness of 0.14 mm and a mesh size of 0.5 mm. Application was carried out using a template having a thickness of 2 mm, and powder was applied using a sieve having a mesh size of 1 mm. Excess powder charged beyond the thickness of the template was removed using a skimmer. After removing the template, the support with the applied powder mixture was pressed using a roller press with a pressure of 0.25 kN / cm. The oxygen consuming electrode was removed from the roller press.

  The oxygen consuming electrode thus produced was used in electrolysis as described in Example 1.

A cell voltage of 2.09 V was measured at a current density of 4 kA / m ² . This value was much larger than the cell voltage in Example 1.

Claims (18)

a) While maintaining the pH constant within a range of 10-12 and maintaining the temperature within a range of 20 ° C to 80 ° C, an aqueous sodium hydroxide solution and a silver nitrate solution were simultaneously added to the receiver, and 0.01 W Precipitating silver oxide by using a mechanical stirrer to introduce stirring energy in the range of / L to 10 W / L;
b) removing the precipitated silver oxide of step a) from the suspension;
c) drying the silver oxide at a temperature in the range of 80 ° C. to 200 ° C., optionally under reduced pressure and optionally under an inert gas atmosphere;
d) A method for producing an oxygen-consuming electrode, comprising the step of further processing the obtained silver oxide together with a conductive support material, a silver particle-containing catalyst and a finely powdered fluorinated polymer to form a planar oxygen-consuming electrode.   The process according to claim 1, wherein energy is introduced in step a) using a propeller stirrer.   The process according to claim 1, wherein the energy input in step a) is from 0.01 to 1 kWh per kg of precipitated product.   The process according to claim 1, wherein the pH of the mixture is maintained in the range of 10.5 to 11.5 in step a).   The process according to claim 1, wherein the temperature of the mixture is maintained in the range of 30C to 70C in step a).   The method of claim 1, wherein the silver oxide of step c) has a d90 of less than 13 μm.   In a further processing step d), 0.5 to 20 parts by weight of fluorinated polymer, 1 to 20 parts by weight of particulate silver and 60 to 98.5 parts by weight of particulate silver oxide are used. The method described.   2. The method according to claim 1, wherein a dry production process is used in the further processing step d).   An oxygen-consuming electrode produced by the method of claim 1, comprising an electrically conductive support, an electrical contact site, and a gas diffusion layer comprising a catalytically active component, wherein the gas diffusion layer is at least An oxygen consuming electrode comprising one fluorinated polymer, particulate silver and particulate silver oxide.   10. The oxygen consuming electrode according to claim 9, comprising silver oxide particles having a d90 of less than 13 [mu] m.   An electrolytic cell for hydrolyzing an alkali metal chloride, comprising the oxygen-consuming electrode according to claim 9 as a cathode.   The agitation energy is in the range of 0.05 W / L to 5 W / L, and the precipitated silver oxide of step a) is removed from the suspension by filtering the suspension and washing the silver oxide one or more times. The method described in 1.   The method according to claim 1, wherein the stirring energy is in the range of 0.1 to 2 W / L.   The method according to claim 2, wherein the propeller stirrer is operated at a stirring speed of 300 to 1000 rpm.   8. The process according to claim 7, wherein in a further processing step d) 2 to 10 parts by weight of fluorinated polymer, 2 to 10 parts by weight of particulate silver and 70 to 95 parts by weight of particulate silver oxide are used.   In a further processing step d), a dry production method is used by pressing a fine powder mixture of silver oxide, silver particle-containing catalyst and fine powder fluorinated polymer together with a conductive support material to form a flat oxygen-consuming electrode. Item 9. The method according to Item 8.   12. The electrolysis cell according to claim 11, wherein the alkali metal chloride is selected from the group consisting of sodium chloride, potassium chloride and mixtures thereof.   The electrolysis cell according to claim 11, wherein the alkali metal chloride is sodium chloride.